Color-photographic proofing process

ABSTRACT

A PROCESS FOR THE MANUFACTURE OF SCREENED COLORED POSITIVE DIRECT-VIEWING IMAGES, WHICH IN THE PRINTING INDUSTRY PERMIT THE RAPID DETECTION OF THE MATCHING OF THE COMPONENT PRINT POSITIVES WHICH THE FINAL PRINTED PRODUCT WILL SHOW IS DISCLOSED.

United States Patent US. CI. 96-14 4 Claims ABSTRACT OF THE DISCLOSURE Aprocess for the manufacture of screened colored positive direct-viewingimages, which in the printing industry permit the rapid detection of thematching of the component print positives which the final printedproduct will show is disclosed.

The present invention relates to a process for the manufacture ofscreened colored positive direct-viewing images, which in the printingindustry permit the rapid detection of the matching of the componentprint posiitves which the final printed product will show. The colorshades of the base colors yellow, magenta and cyan are so controlled bythe copying process that they are matched to the printing inks.

The proof printing of a photolithographic print is even today still atime-consuming and expensive matter. Various attempts have already beenmade to produce proof prints of correct color and correct tone valuesmore rapidly and more cheaply, avoiding the customary proof printingapproach. Hitherto, however, the methods are too expensive, or theresults are not satisfactory.

Particular problems arise in the production of so-called color proofs onphotographic multi-color material, because in the graphic industry aproofing system has to provide variability of the base color shades andcolor densities.

A process has now been discovered which fulfils this requirement andyields images which come very close to the printed product.

The subject of the invention is, accordingly, a process for themanufacture of a screened, photographic color copy simulating amulti-color print, preferably multicolor oliset print, in which thescreened positive color separation components of the original, whichappertain to the individual colors, are exposed together with thescreened black separation component and, if appropriate, the blackseparation component alone is additionally exposed onto alight-sensitive positively working colorphotographic material,characterized in that (a) at least one of the color separationcomponents together with (b) the black separation component and (c) atleast partially together with at least one of the remaining colorseparation components, is exposed with the light of the colorappertaining to the color separation component (a) onto thelight-sensitive color-photographic material, and the material thusexposed is processed to give a screened, pos itive direct-viewing imagewhich possesses base colors matching the printing inks.

In the process according to the invention the procedure is thus that thescreened, positive color separation components of the original (b1ue=B,green=G, red=R) and the black separation component (black=-S) of theoriginal are brought into register with one another as combinations BS,GS and RS, and are then successively exposed, in optional sequence, withthe corresponding filters (blue=b, green=g, red=r) onto alight-sensitive, positively working photographic material in thecombinations BS-b, GS-g, RS-r and, if appropriate, additionally S alone,the improved matching of the color impression of the color copy to theprinting inks being achieved in that additionally, at least one of thefollowing combinations is exposed: BGS-b, BGS-g, BRS-b, BRS-r, GRS-g,GRS-r, BPRS-b, BGRS-g or BGRS-r.

The exposures, without and with a 2nd and optionally 3rd"co1orseparation component (c) are computed from the densitometric measurementof the printing ink and from the colors on the photographic copy.

In the process according to the invention, the procedure followed isthus that, depending on the measured color deviation of the individualbase colors of the color proof from the printing ink, a second and, ifappropriate, a third color separation screened positive is exposed to agreater or lesser extent together with the color separation positive tobe copied, and that this is done in such a way that the proportion ofexposure of the additional second or third color separation componentwith the main color separation component is together as a rule 10 to100%, preferably 40 to of the total exposure time of the first colorseparation component.

The second possibility of adapting the proof to the printing conditionsis, in addition to varying the color shades, adjusting the maximumdensities of the individual base colors, or reduction, to the printcolor density. For this purpose, an exposure through the black printpositive is made with the color filter complementary to the reducingcolor. The exposed material is subsequently developed to give a positivedirect-viewing image.

The process according to the invention is above all suitable forsimulating screened multicolor ofiset-printed products.

Photographic material for the silver dye bleach process has provedparticularly advantageous for the process according to the invention,since it permits colored images to be produced wherein the colorscorrespond relatively well to the printing inks. A further advantage ofthe photographic material for the silver dye bleach process is that itpermits positive copies of positive color separation components to beproduced with ease. The present process is, however, not restricted tophotographic material for the silver dye bleach process, and materialused, for example, for the dye development process is also suitable.

The color separation components required for the process according tothe invention, for example the green, red and blue filter separationcomponent, as well as the black separation component, are produced inthe usual and known manner. Since these separation components are in theform of monochrome, and generally black-andwhite, diapositives, thechoice of the copying lights in photographic further processing now onlydepends on the spectral sensitivities of the copying material.

The color separation component positives, which are in most casesblack-and-white, correspond to the positives usually employed in screenoifset printing technique. These screen positives are as a rule contactcopies or enlargements of screened or continuous-tone separationnegatives, and in the cast of continuous-tone negatives a contact screenmust be copied with them. The continuoustone or screen negatives areproduced with color filters,

either conventionally or via so-called scanners. The color retouchingand correction of the color separation components is adapted to theworks colour scale of the For comparison, the printing ink is measuredwith the photographic color proo with and without mixing-in individualprinting works.

of a 2nd or 3rd color separation component, in a densitometer. Thefollowing values are found:

Relative densities N orEs.-I=Here the printing inks used are measured.II=These are measured values of a "color proof" without mixing-in.III=This represents the chosen subdivision of thr exposure to blue lightinto a part exposure with blue filter positive plus black print positiveand a 60% part exposure with blue filter positive plus black printpositive plus green filtee positive, with the exposure of thecombinations green filter positive plus black print positive and redfilter positive lus black print positive being unchanged. The exposuretimes are co nputedas follows: t e exposure to blue light with the bluefilter positive and the black print positive is 4 seconds for acorrectly exposed image. This exposure is now subdivided into a partexposure of 1.6 seconds (40%) for the blue filter positive and blackprint positive and 2.4 seconds (60%) for the second part exposure of theblue filter positive, green filter positive and black print positive.

EXAMPLE 1 If a warmer (yellower) magenta printing ink is used, the colorproof can be adapted to the printing ink by increasing the proportion ofyellow in the magenta. The procedure is as follows:

Psi-t exposure (40%) 1. Blue filter positive Black print positive Totalblue Part exposure (607 2 Blue filter positive exposure Black printpositive Green filter positive Total exposure 3 Green filter positive522:

Black print positive exposure 4 Red filter positive gg Black printpositive exposure Effective relative exposure times:

(1) 1.6 seconds (2) 2.4 seconds (3) 2 seconds (4) 2 seconds.

The blue filter positive is combined in register with the black printpositive and copied onto the emulsion sensitive to blue, by means of apart exposure with blue light. The green filter positive is then addedthereto and the second part exposure effected with blue light. For thegreen filter exposure, the green filter positive and the black printpositive are used, and for the red exposure the red filter positive isagain used with the black print positive.

After these exposures, the color-photographic material is developed bythe silver dye bleach process to give a positive direct-viewing image,which comes close to the printed product produced with the sameseparation components.

EXAMPLE 2 If warmer magenta and cyan printing inks are used, theprocedure for adapting the color proof is as follows:

Part exposure (40%) 1. Blue filter positive Black print positive TotalPart exposure (60%) blue Blue filter positive exposure 2. Black printpositive+ Green filter positive Red filter positive Total exposure Greenfilter ti Total 3 green Black print positive exposure 4 Red filterpositive 123 Black print positive exposure Eifective relative exposuretimes:

(1) 1.6 seconds (2) 2.4 seconds (3) 4 seconds (4) 4 seconds.

As in Example 1, there are 2 exposures using the blue filter onto aphotographic material for the silver dye bleach process:

The first with the blue filter and black print positive and the secondexposure additionally with the green filter positive and red filterpositive. The green and red exposures remain the same as in Example 1.After the exposures, a positive direct-viewing image is obtained, whichcomes close to the printed product produced with the same separationcomponents.

Relative density values measured as in Example 1:

tive plus green filter positive plus black pn'nt positive.

The blue exposure is again subdivided into 40% exposure for the firstpart exposure of the blue filter positive and black print positive at60% exposure for the second part exposure, in which blue filter, greenfilter and red filter positives and the black print positive are used.In this way yellow is mixed into the magenta and cyan color of the colorproof.

As regards the density values it should be mentioned that a trained eyecan detcet a difference of about 0.03 density unit.

EXAMPLE 3 Instead of the customary cyan color shade, a reddish cyan isdesired, in which additionally the maximum density of the cyan layermust also be reduced. The procedure is here as follows:

- Total Blue filter positive Black print positive Eigg Part exposure(75%) 2. Green filter positive Black print positive Total Part exposure(257 green 3 Green filter positirfe exposure Total Black print positiveexposure Red filter positive 4 Red filter positive Red Black printpositive exposure 5. Black print positive ga Eifective exposure times:

(1) 4 seconds (2) 3 seconds (3) lsecond (4) 4 seconds (5) .05 second.

Step 5 reduces the maximum density of the cyan layer.

The screened separation component positives of an original color imageare copied onto a photographic material for the silver dye bleachprocess in the same way as described in Example 1. The exposure times ofthe part exposure depend again on the desired percentage mixing of onebase color into the other base color. Equally, the exposure to reducethe cyan density depends on the desired change.

These exposures give a positive direct-viewing image which comes closeto the printed product. produced with the same separation components.

What is claimed is:

1. In a process for the manufacture of a screened, photographic colorcopy simulating a multi-color print, in Which the screened positivecolor separation components of the original, which appertain to theindividual colors, are exposed together with the screened blackseparation component and, if appropriate, the black separation componentalone is additionally exposed onto a light-sensitive positively workingsilver dye bleach color-photographic material, the improvement whichcomprises exposing at least one of the color separation components (i)together with the black separation component and at least partiallytogether with at least one of the remaining color separation components(ii) with the light of the color appertaining to the color separationcomponent (i) onto the light-sensitive silver dye bleachcolor-photographic material, and processing the material thus exposed togive a screened, positive direct-viewing image which possesses basecolors matching the printing inks.

2. Process according to claim 1, which comprises coexposing the secondcolor separation component (ii) for 10 to 100% of the total exposuretime of the color separation component (i).

3. Process according to claim 2, which comprises coexposing the secondcolor separation component (ii) for 40 to of the total exposure time ofthe color separation component (i). i

4. Process according to claim 3, which comprises simulating with thephotographic color copy a multi-color planographic printing product.

References Cited UNITED STATES PATENTS 2,841,492 7/1958 Greham 96-303,576,627 4/1971 Wirth 9623 NORMAN G. TORCHIN, Primary Examiner A. T.SURO PICO, Assistant Examiner US. Cl. X.R. 9617, 45, 59

